Compound semiconductor device, method for producing same, and resin-sealed type semiconductor device

ABSTRACT

In a semiconductor element having a compound semiconductor layer epitaxially grown on a silicon substrate, an object is to suppress generation of deficiency or problems of reliability deriving from the ends of the element that are generated when dividing into semiconductor devices by dicing. A compound semiconductor layer epitaxially grown on a silicon substrate is formed via a buffer layer made of aluminum nitride. In the periphery of the semiconductor device, a scribe lane is present to surround a semiconductor element region. Along the scribe lane, the aluminum nitride layer is covered with a coating film for protection against humidity and moisture.

RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 15/823,245 filed on Nov. 27, 2017, which is aDivisional application of U.S. patent application Ser. No. 14/880,975,filed on Oct. 12, 2015, now U.S. Pat. No. 9,865,679, which is aContinuation of International Patent Application No. PCT/JP2014/001691,filed on Mar. 25, 2014, which in turn claims the benefit of JapaneseApplication No. 2013-086339, filed on Apr. 17, 2013, the entiredisclosures of which Applications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a compound semiconductor device inwhich a compound semiconductor layer epitaxially grown on a siliconsubstrate is formed via a buffer layer made of aluminum nitride, as wellas to a method for producing the same, and a resin-sealed typesemiconductor device.

2. Description of the Related Art

In recent years, as a material of a semiconductor device, development ofa nitride-based semiconductor material, which is a wide-bandgapsemiconductor, is actively carried out. As a characteristic feature ofthe wide-bandgap semiconductor, it can be mentioned that thewide-bandgap semiconductor has an insulation breakdown voltage largerthan that of silicon (Si), which is a general semiconductor, by an orderof magnitude.

With conventional Si, a drift layer in which electrons travel needs tobe made long in order to obtain a power semiconductor device having ahigh breakdown voltage. In contrast, gallium nitride (GaN) provides anequivalent breakdown voltage with a short drift layer (about 1/10 ofSi). In this case, when a situation of allowing an electric current toflow in the semiconductor device is considered, the drift layer becomesa resistance layer, so that the on-resistance of the semiconductordevice becomes smaller when the drift layer is shorter. Theoretically,assuming that the mobility and the dielectric constant of asemiconductor are of the same degree, the on-resistance of thesemiconductor device exhibiting a certain predetermined breakdownvoltage is inversely proportional to the cube of the insulationbreakdown electric field that the semiconductor material has. In otherwords, with the same chip area, an on-resistance lower by about 1/1000can be achieved in a GaN device as compared with a Si device.

A nitride-based semiconductor material can form various mixed crystalswith GaN, aluminum nitride (AlN), and indium nitride (InN), so that thenitride semiconductor material can make a heterojunction as with aconventional arsenic semiconductor material such as gallium arsenic(GaAs). In particular, the heterojunction of the nitride-basedsemiconductor has a characteristic feature such that high concentrationof carriers are generated at the interface by spontaneous polarizationor piezo-polarization even in a state in which doping of impurities isabsent. As a result, in a lateral-type device in which an electriccurrent is allowed to flow in a direction parallel to the siliconsubstrate using the heterojunction of GaN/AlGaN, a device for largeelectric power having a low on-resistance with a large electric currentcan be achieved.

Further, the nitride-based semiconductor material can be epitaxiallygrown on a silicon substrate via a buffer layer made of aluminumnitride. In other words, though it is necessary to use an expensivesilicon carbide (SiC) substrate with the same wide-bandgap semiconductormaterial in the case of a SiC device, it is possible to use a siliconsubstrate in the case of a nitride-based semiconductor device, so thatreduction of costs and increase in the diameter can be achieved.

In the meantime, the nitride-based semiconductor device in which thenitride-based semiconductor layer has been formed on the siliconsubstrate (wafer) is divided into semiconductor devices by performingdicing along a scribe lane as with a conventional silicon device or GaAsdevice. In this dicing step, after the wafer is bonded to a dicing tape,the wafer is subjected to a cutting process along the scribe lane whilea thin-type grindstone having a disk shape, which is known as a dicingblade, is rotated at a high speed.

In this dicing step, fragmentation, cracks, and crystal defects of thesemiconductor layer, which are called chipping, are generated in thescribe lane if a blade kind, a rotation number, a dicing speed, and thelike are not appropriately selected. Further, when the chipping orcrystal defects generated in the scribe lane reach an element formationregion within the semiconductor device, deficiency of electriccharacteristics or deficiency of reliability caused by penetration ofmoisture is generated.

Generally, the blade kind, the rotation number, and the dicing speed areappropriately selected in order to eliminate deficiency generation inthe semiconductor device caused by chipping or crystal defects. A scribelane width is set so that the deficiency may remain within the scribelane even when chipping or crystal defects are generated or whenmoisture penetrates via the buffer layer.

In the silicon device, a structure of suppressing chipping in thesemiconductor device is known. For example, PTL 1 discloses a structurein which a film is formed on a scribe lane between a plurality ofsemiconductor elements formed on a semiconductor wafer. According tothis structure, progression of a stress that generates the chipping canbe absorbed or alleviated with a wall of this film, so that suppressionof the chipping can be expected.

On the other hand, in a nitride-based compound semiconductor device, astructure in which an aluminum nitride layer is formed as a surfaceprotection film is known. For example, PTL 2 discloses a structure inwhich an AlN layer is formed as a surface protection film on anupper-side surface of an AlGaN layer. According to this productionmethod, the upper-side surface of the AlGaN layer is covered with theAlN layer before cracks are generated, so that it can be expected thatthe surface will be a flat surface without cracks.

CITATION LIST Patent Literatures

PTL 1: Unexamined Japanese Patent Publication No. 2006-302939

PTL 2: Unexamined Japanese Patent Publication No. 2006-156429

However, in a nitride-based semiconductor device having a nitride-basedsemiconductor layer epitaxially grown on a silicon substrate, chippingor crystal defects at the end of the nitride-based compoundsemiconductor are liable to be generated to a degree more than in thesilicon device or the GaAs device when the nitride-based semiconductorlayer is subjected to dicing. Therefore, there are cases in which thegeneration of deficiency and deterioration of reliability caused bychipping or crystal defects cannot be sufficiently suppressed by ageneral procedure such as described above. The reason therefor is asfollows. Due to the difference of lattice constant and thermal expansioncoefficient between silicon and the nitride-based semiconductor such asGaN, a large stress is generated near an interface between the siliconsubstrate and the nitride-based semiconductor layer. When a mechanicalshock at the time of dicing is applied near the interface between thesilicon substrate and the nitride-based semiconductor layer, cracks andcrystal defects are generated with this interface serving as a startingpoint.

Further, the larger the thickness of the epitaxially grown nitride-basedsemiconductor layer is, the larger the stress will be. Accordingly, thenumber of sites where chipping or crystal defects are generatedincreases, and the size of chipping or crystal defects also increases.

FIG. 5 shows a schematic plan view when a nitride-based semiconductorlayer epitaxially grown on a silicon substrate is subjected to dicing.In FIG. 5, a large number of minute chippings are generated along thedicing line. Among these, some chippings are generated going beyond thescribe lane and reaching the surface protection film of the element, asshown in FIG. 6. In this case, the outlook of the semiconductor devicewill be also deficient.

The buffer layer “aluminum nitride” used in epitaxially growing thenitride-based semiconductor layer on the silicon substrate reacts withmoisture to provoke a reaction of AlN+3H₂O→Al(OH)₃+NH₃. This causes aproblem in that the properties are deteriorated by the humidity ormoisture penetrating through the end of the element.

In the case of sealing the nitride-based semiconductor element with aresin (including the cases of “incorporation into acomponent-incorporated substrate” and “under/side-filling sealing offlip-chip mounting”), there are problems in that exfoliation isgenerated at the interface to the sealing resin due to exposure of thenitride-based semiconductor epitaxial film, which has a poorclose-adhesiveness to the resin, at the end the element.

Here, in a nitride-based semiconductor device having a nitride-basedsemiconductor layer epitaxially grown on a silicon substrate, it can beconsidered to prevent chipping, crystal defects, or moisture penetrationinto the semiconductor element from reaching an active region of theelement by widely setting the scribe lane width further to be about 150μm. However, when the scribe lane width is increased, the number ofchips that can be collected from one sheet of wafer will be smaller.

There can be considered a method of removing the nitride-basedsemiconductor layer in the scribe lane by dry etching or the like beforethe scribe lane is diced. However, in order to achieve an element havinga high breakdown voltage of not less than 500 V, the thickness of thenitride-based semiconductor layer having a high resistance that is grownon the electrically conductive silicon substrate needs to be about notless than 4 μm, so that it is difficult to remove such a thicknitride-based semiconductor layer by etching.

SUMMARY OF THE INVENTION

The present disclosure has been made in view of such circumstances, andan object thereof is to provide a semiconductor device having anitride-based semiconductor layer epitaxially grown on a siliconsubstrate or the like on the surface side, wherein the semiconductordevice has a structure in which the chipping and crystal defectsgenerated at the time of dicing can be suppressed even when the scribelane width is not set to be large or when the nitride-basedsemiconductor layer of the scribe lane is not etched, and in whichaluminum nitride is not exposed at the end of the element.

In order to solve the aforementioned problems, a compound semiconductordevice according to the disclosure of the present application is acompound semiconductor device which is a compound semiconductor chiphaving a compound semiconductor layer epitaxially grown on a substratevia an aluminum nitride layer, wherein the aluminum nitride layerlocated below the compound semiconductor layer in the periphery of anelement is covered with an amorphous layer or a polycrystal layer.

This allows that the chipping, crystal defects, and moisture penetrationcan be suppressed in a semiconductor device that has a nitride-basedsemiconductor layer epitaxially grown on a silicon substrate and isdiced along the scribe lane. In other words, when the chipping, crystaldefects, and moisture penetration generated from the dicing surface thathas been diced along the scribe lane spread, a structure body ofsuppressing the chipping, crystal defects, and moisture penetration thathas been formed at the end of the nitride-based semiconductor layer inthe scribe lane suppresses this extension of the chipping, crystaldefects, and the like.

The nitride-based compound semiconductor device, the method of producingthe same, and the resin-sealed type semiconductor device according tothe disclosure of the present application provide an advantage suchthat, when the chipping, crystal defects, and moisture penetrationgenerated from the dicing surface that has been diced along the scribelane spread, a structure body of suppressing the chipping, crystaldefects, and moisture penetration that has been formed at the end of thenitride-based semiconductor layer in the scribe lane can suppress thisextension of the chipping, crystal defects, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a semiconductor device according to oneexemplary embodiment;

FIG. 2A is a schematic view illustrating a semiconductor wafer beforeand after dicing, in which a plurality of semiconductor devicesaccording to one exemplary embodiment are arranged;

FIG. 2B is a schematic view illustrating a semiconductor wafer beforeand after dicing, in which a plurality of semiconductor devicesaccording to one exemplary embodiment are arranged;

FIG. 2C is a schematic view illustrating a semiconductor wafer beforeand after dicing, in which a plurality of semiconductor devicesaccording to one exemplary embodiment are arranged;

FIG. 3A is a view showing a photograph of a cross-section around ascribe lane before dicing;

FIG. 3B is a view showing an enlarged photograph of a cut surface afterthe scribe lane of FIG. 3A has been cut with a blade;

FIG. 4A is a view showing a photograph of a cross-section around ascribe lane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4B is a view showing a result of element analysis around a scribelane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4C is a view showing a photograph of a cross-section around ascribe lane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4D is a view showing a result of element analysis around a scribelane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4E is a view showing a photograph of a cross-section around ascribe lane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4F is a view showing a result of element analysis around a scribelane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4G is a view showing a photograph of a cross-section around ascribe lane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 4H is a view showing a result of element analysis around a scribelane in which structure bodies for suppressing chipping, crystaldefects, and moisture penetration have been formed by fusion, reaction,and making an amorphous state down to a silicon substrate using a laserbeam;

FIG. 5 is a schematic plan view after a conventional semiconductordevice having a nitride-based semiconductor layer has been formed bydicing; and

FIG. 6 is a schematic plan view in which deficiency caused by chippinghave been generated in a conventional semiconductor device having anitride-based semiconductor layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, exemplary embodiments of a compound semiconductor deviceaccording to the disclosure of the present application, a method forproducing the same, and a resin-sealed type semiconductor device will bedescribed with reference to the attached drawings.

FIG. 1 is a plan view of a semiconductor device according to the presentexemplary embodiment. This semiconductor device has been fabricated bydicing a semiconductor wafer in which a plurality of semiconductordevices is arranged.

FIGS. 2A, 2B, and 2C are cross-sectional views each illustrating thesemiconductor wafer before and after dicing, in which a plurality of thesemiconductor devices shown in FIG. 1 are arranged, where near scribelane 10 is shown. Referring to FIGS. 2A, 2B, and 2C, in thesemiconductor device, nitride-based semiconductor layer 2 including abuffer layer is disposed over a whole surface of silicon substrate 1. Inthe present exemplary embodiment, the substrate is made of silicon;however, the substrate may be made of any of silicon, sapphire andsilicon carbide. On silicon substrate 1, nitride-based semiconductorlayer 2 is formed to extend across a semiconductor element formationregion and scribe lane 10. Nitride-based semiconductor layer 2 is alayer formed by epitaxially growing a nitride-based semiconductor onsilicon substrate 1. Here, in a semiconductor element region having arectangular shape, nitride-based semiconductor layer 2 includes a bufferlayer made of AlN or AlGaN, an operation layer made of GaN or AlGaN, andthe like.

Further, referring to FIGS. 1, 2A, 2B, and 2C, surface protection film 3is disposed in the rectangular semiconductor element region on thesurface of nitride-based semiconductor layer 2. Surface protection film3 is made, for example, of SiN, and is formed by plasma CVD (Chemicalvapor deposition). In the periphery of the semiconductor device, scribelane 10 is present to surround this semiconductor element region.Further, referring to FIG. 1, first pad 21, second pad 22, andcomb-shaped interconnect 23 are formed with common interconnect metallayer 4 on surface protection film 3 in the semiconductor elementregion. Interconnect metal layer 4 has a structure in which Ti layer 4 aand Au layer 4 b (not illustrated) are stacked, and Au layer 4 b hasbeen formed by plating on Ti layer 4 a.

The thickness of each layer is, for example, such that the thickness ofTi layer 4 a is 0.1 μm, and the thickness of Au layer 4 b is 5 μm. Tilayer 4 a which is a lower layer has a good close adhesion property tonitride-based semiconductor layer 2 and has a function of strengtheninga close adhesion between Au layer 4 b and nitride-based semiconductorlayer 2.

A part of nitride-based semiconductor layer 2 is present in ring-shapedscribe lane 10 that exists in the periphery of the semiconductor device.Referring to FIGS. 2A, 2B, and 2C, first structure body 11, secondstructure body 12, third structure body 13, and fourth structure body 14that suppress chipping, crystal defects, and moisture penetration areformed on the part of nitride-based semiconductor layer 2 that ispresent in scribe lane 10. Referring to FIG. 1, first structure body 11,second structure body 12, third structure body 13, and fourth structurebody 14 that suppress chipping, crystal defects, and moisturepenetration are formed along scribe lane 10. In other words, firststructure body 11, second structure body 12, third structure body 13,and fourth structure body 14 that suppress chipping, crystal defects,and moisture penetration are formed in a ring shape in the periphery ofthe semiconductor device. First structure body 11 produces an effect offorming a protection film over the whole buffer layer reaching a pointof contact to silicon substrate 1 by being formed widely around a centerof the scribe lane with which a dicing blade comes into contact. Secondstructure body 12 is one formed by re-adhesion after being scattered byablation phenomenon with a laser beam, and covers a part from around thecenter of the scribe lane up to a region where the buffer layer is notexposed at an end. Third structure body 13 produces an effect ofprotecting the buffer layer against humidity and moisture by beingformed to cover the end of the buffer layer. Fourth structure body 14 isformed on the surface of a region remaining at the end of the chip afterdicing, and produces an effect of improving the close adhesion propertyat the interface to a sealing resin in the case of sealing with theresin (including the cases of “incorporation into acomponent-incorporated substrate” and “under/side-filling sealing offlip-chip mounting”). The structures of first structure body 11, secondstructure body 12, third structure body 13, and fourth structure body 14that suppress chipping, crystal defects, and moisture penetration aremade by first structure body 11 which is a groove/recess reachingsilicon substrate 1, second structure body 12 which is an area obtainedby partly making the nitride-based compound semiconductor layer beamorphous, third structure body 13 which is a coating film forprotecting the “aluminum nitride” barrier layer against humidity andmoisture, and fourth structure body 14 which is a nitride-based compoundsemiconductor layer obtained by surface-roughening (0.05 μm to 1.0 μm)(See FIGS. 2A, 2B, and 2C). Here, first structure body 11, secondstructure body 12, third structure body 13, and fourth structure body 14that suppress chipping, crystal defects, and moisture penetration may beformed in a continuous ring shape along ring-shaped scribe lane 10;however, referring to FIG. 1, first structure body 11, second structurebody 12, third structure body 13, and fourth structure body 14 may beseparated at a corner part or the like of the semiconductor device. Achipping suppression effect is produced even when the width of firststructure body 11, second structure body 12, third structure body 13,and fourth structure body 14 that suppress chipping, crystal defects,and moisture penetration is small; however, the effect is larger whenthe width is larger. However, the scribe lane width will be large whenthe width of first structure body 11, second structure body 12, thirdstructure body 13, and fourth structure body 14 that suppress chipping,crystal defects, and moisture penetration is set to be too large. Thewidth of first structure body 11, second structure body 12, thirdstructure body 13, and fourth structure body 14 that suppress chipping,crystal defects, and moisture penetration is suitably 5 μm to 25 μm,more preferably 10 μm to 20 μm.

Next, a dicing step will be described which is a characteristic step inthe method for producing a compound semiconductor device according tothe disclosure of the present application.

The semiconductor device shown in FIG. 1 is fabricated by dicing thesemiconductor wafer shown in FIGS. 2A, 2B, and 2C along scribe lane 10and dividing the semiconductor wafer. This dicing step is carried out asfollows: after the semiconductor wafer is bonded to a dicing tape,scribe lane 10 is made to abut against nitride-based semiconductor layer2 and the semiconductor wafer is subjected to a cutting process bymoving the semiconductor wafer in a front-and-back direction of a papersheet in FIGS. 2A, 2B, and 2C while a thin-type grindstone having a diskshape, which is known as a dicing blade, is rotated at a high speed. Inthis dicing step, a kind of the blade to be used, a rotation number, adicing speed, and the like are appropriately set. A blade width of thedicing blade is about 20 μm to 30 μm, and the width of scribe lane 10that is set in the semiconductor wafer is about 50 μm to 100 μm.

Next, with respect to means, mechanism, and the like for ensuring astable quality in the dicing step, the effect of suppressing thechipping, crystal defects, and the like by first structure body 11,second structure body 12, third structure body 13, and fourth structurebody 14 that suppress the chipping, crystal defects, and moisturepenetration, that is, the effect of suppressing the chipping, crystaldefects, and the like in the nitride-based semiconductor device havingthe above configuration will be described.

In the above semiconductor device, nitride-based semiconductor layer 2is formed to extend across the semiconductor element formation regionand scribe lane 10 on silicon substrate 1. Therefore, when chipping,crystal defects, and the like are generated from a dicing surface indicing nitride-based semiconductor layer 2 and silicon substrate 1 alongscribe lane 10, the chipping, crystal defects, and the like spread tothe semiconductor element formation region. However, because firststructure body 11, second structure body 12, third structure body 13,and fourth structure body 14 that suppress the chipping, crystaldefects, and moisture penetration are formed on nitride-basedsemiconductor layer 2 in scribe lane 10, progression of the chipping,crystal defects, and the like is hindered by first structure body 11,second structure body 12, third structure body 13, and fourth structurebody 14 that suppress the chipping, crystal defects, and moisturepenetration.

Here, first structure body 11, second structure body 12, third structurebody 13, and fourth structure body 14 that suppress the chipping,crystal defects, and moisture penetration, though being formed at an endof the nitride-based semiconductor layer, have a groove/recess thatreaches silicon substrate 1, so that damages at the time of dicing areless likely to be propagated to the nitride-based semiconductor layer,and the effect of the function of suppressing the chipping, crystaldefects, and moisture penetration is large. Therefore, spreading of thechipping, crystal defects, and the like to a semiconductor element sidecan be sufficiently suppressed.

Further, first structure body 11, second structure body 12, thirdstructure body 13, and fourth structure body 14 that suppress thechipping, crystal defects, and moisture penetration are formed in a lineshape along a boundary between the semiconductor element formationregion and the scribe lane, so that the effect of preventing thechipping, crystal defects, and the like can be sufficiently obtainedwhile suppressing the width of scribe lane 10 to be small.

Next, a method for irradiating a laser beam onto scribe lane 10 on whicha nitride-based semiconductor film has been formed (film thickness being4 μm) will be described.

First, a water-soluble protection film is applied by rotation onto awafer that is in a state in which surface protection film 3 has beenformed on a nitride-based semiconductor, and then a laser beam isirradiated along scribe lane 10. In the present exemplary embodiment,the laser beam is allowed to scan in a direction perpendicular to a(111) plane of silicon substrate 1; however, the laser beam may beallowed to scan in other directions. During this process, firststructure body 11, second structure body 12, third structure body 13,and fourth structure body 14 that suppress chipping, crystal defects,and moisture penetration can be formed to have a large width when thelaser beam is allowed to scan for a plurality of times while shifting aposition of the laser beam little by little along the scribe lane. Forexample, when a processing width per one time of scanning by the laserbeam is set to be 10 μm to 30 μm and the position is shifted fromoutside of the scribe lane towards a center with a shifting pitch of 5μm to 20 μm, then a finished processing width obtained by scanning for aplurality of times can be made to be 40 μm to 90 μm. Conditions of thelaser beam during this process are set in such a manner that, inpower-fixed control, a pulse frequency is 40 kHz to 100 kHz; an outputis 2 W to 7 W; a sending speed is 100 mm/sec to 400 mm/sec; and a laserfocus position ranges from a working surface to a place located away by0.2 mm thereabove. Thereafter, by washing a wafer surface with purewater, a scattered substance adhering onto an active region can beremoved together with the water-soluble protection film. At this time,because the water-soluble protection film has been removed by the laserbeam at a chip end, the scattered substance can be allowed to remain asa protection film selectively at the chip end only. Because thescattered substance is scattered away by ablation phenomenon with thelaser beam and cooled in a short period of time, the scattered substancebecomes an amorphous layer or a polycrystal layer having peaks andvalleys with an average pitch of 0.05 μm to 1.0 μm on a surface thereof.Thereafter, scribe lane 10 is made to abut against nitride-basedsemiconductor layer 2 and the wafer is subjected to a cutting process bymoving the wafer in a front-and-back direction of a paper sheet in FIGS.2A, 2B, and 2C while a thin-type grindstone having a disk shape, whichis known as a dicing blade, is rotated at a high speed. The blade widthof the dicing blade is about 20 μm to 30 μm, and the width of scribelane 10 that is set in the semiconductor wafer is about 50 μm to 100 μm.

The compound semiconductor device of the present exemplary embodiment isa compound semiconductor device in which the amorphous layer or thepolycrystal layer contains at least silicon or aluminum or both ofsilicon and aluminum. Therefore, because any of silicon and aluminum hasa property of being less liable to proceed to a deep part even whenreacting with moisture, the amorphous layer or the polycrystal layerproduces an effect of protecting the buffer layer “aluminum nitride”against moisture.

The compound semiconductor device of the present exemplary embodiment isa compound semiconductor device in which the amorphous layer or thepolycrystal layer contains silicon at not less than 1 at %. Therefore,because a material containing silicon at more than 1 at % has a furthermore enhanced property of being less liable to proceed to the deep parteven when reacting with moisture, the amorphous layer or the polycrystallayer produces a further more enhanced effect of protecting the bufferlayer “aluminum nitride” against moisture.

FIGS. 3A and 3B are views each showing a photograph of a cross-sectionaround scribe lane 10 in which first structure body 11, second structurebody 12, third structure body 13, and fourth structure body 14 thatsuppress chipping, crystal defects, and moisture penetration have beenformed. FIG. 3A is a view showing a photograph of a cross-section aroundscribe lane 10 before dicing, and FIG. 3B is a view showing an enlargedphotograph of a cut surface after scribe lane 10 of FIG. 3A has been cutwith a blade.

FIGS. 4A, 4C, 4E, and 4G are views each showing a photograph of across-section around a scribe lane in which structure bodies forsuppressing chipping, crystal defects, and moisture penetration havebeen formed by fusion, reaction, and making an amorphous state down tosilicon substrate 1 using a laser beam. FIGS. 4B, 4D, 4F, and 4H areviews each showing a result of element analysis around a scribe lane inwhich structure bodies for suppressing chipping, crystal defects, andmoisture penetration have been formed by fusion, reaction, and making anamorphous state down to silicon substrate 1 using a laser beam. A secondspectrum shown in FIGS. 4A and 4B and a third spectrum shown in FIGS. 4Eand 4F show element analysis data (EDX (Energy Dispersive X-ray) method)of second structure body 12 and third structure body 13. A firstspectrum shown in FIGS. 4C and 4D shows element analysis data (EDXmethod) of nitride-based semiconductor layer 2. A fourth spectrum shownin FIGS. 4G and 4H shows element analysis data (EDX method) of siliconsubstrate 1. From the second spectrum and the third spectrum, it will beunderstood that second structure body 12 and third structure body 13contain silicon and aluminum. Also, in the present data, silicon is amajor constituent element, where the second spectrum shows 25.57 at %,and the third spectrum shows 81.35 at %.

Here, in the present exemplary embodiment, an example using siliconsubstrate 1 has been described. However, even with use of a sapphiresubstrate or a silicon carbide substrate, a large stress is generateddue to difference in lattice constant or thermal expansion coefficientwhen a nitride-based semiconductor layer is grown on the substrate.Therefore, even when such a substrate is used, a similar effect can beobtained by forming first structure body 11, second structure body 12,third structure body 13, and fourth structure body 14 that suppress thechipping, crystal defects, and moisture penetration along the scribelane, in the same manner as in the above-described exemplary embodiment.

At the time of fusion, reaction, and making an amorphous state down tosilicon substrate 1 using a laser beam, a protection coating film can besimultaneously formed at the end of the aluminum nitride layer whenconditions for allowing the protection coating film to re-adhere to theend of the aluminum nitride layer by ablation phenomenon (tripled YAGlaser (wavelength of the laser beam being 355 nm)) are selected, wherebyan increase in the number of production steps and an increase in theproduction costs can be restrained to a minimum degree.

The nitride-based semiconductor layer of the compound semiconductordevice according to the disclosure of the present application may beformed to extend across the semiconductor element formation region andthe scribe lane on silicon substrate 1. This allows that the chipping,crystal defects, and the like can be prevented well by the structurebodies that suppress the chipping, crystal defects, and moisturepenetration.

The structure bodies that suppress the chipping, crystal defects, andmoisture penetration are preferably formed in a line shape along aboundary between the semiconductor element formation region and thescribe lane. This allows that the chipping, crystal defects, and thelike can be prevented while suppressing the width of the scribe lane tobe small.

The above structure bodies that suppress the chipping, crystal defects,and moisture penetration may also have a configuration of having aregion that has been turned amorphous, having a protection coating filmat the end of the aluminum nitride layer, or having a region obtained bysurface-roughening (0.05 μm to 1.0 μm) of the nitride-based compoundsemiconductor.

The above structure bodies that suppress the chipping, crystal defects,and moisture penetration can produce similar effects even when a regionis formed by fusion, reaction, and making an amorphous state down tosilicon substrate 1 using a laser beam.

The above structure bodies that suppress the chipping, crystal defects,and moisture penetration can produce similar effects even by allowing acompound having a similar effect to re-adhere to a sidewall by usingplasma etching method.

The structure bodies that suppress the chipping, crystal defects, andmoisture penetration, though being formed at an end of the nitride-basedsemiconductor layer, have a groove/recess that reaches silicon substrate1, so that damages at the time of dicing are less likely to bepropagated to the nitride-based semiconductor layer, and the effect ofthe function of suppressing the chipping, crystal defects, and moisturepenetration is large.

Therefore, even when chipping, crystal defects, and the like aregenerated near the interface between the substrate and the nitride-basedsemiconductor layer, the chipping, crystal defects, and the like areprevented from spreading to the semiconductor element side, so thatelectrical deficiency of the semiconductor element in the semiconductordevice is eliminated. Simultaneously, reliability is improved, andfurther, yield of the semiconductor device is improved. Because there isno need to set the width of the scribe lane to be large, the number ofsemiconductor devices per wafer can be ensured.

The nitride-based compound semiconductor device, the method forproducing the same, and the resin-sealed type semiconductor deviceaccording to the disclosure of the present application provide anadvantage such that, even when a semiconductor device in which anitride-based semiconductor layer is formed on a semiconductor wafersuch as a silicon substrate is used, the chipping, crystal defects, andmoisture in the dicing step can be prevented from reaching the activeregion of the element without increasing the width of the scribe lane,whereby the electric characteristics and reliability of thesemiconductor device can be ensured.

Therefore, the present disclosure provides a technique useful inachieving a semiconductor device for electric power that has a highbreakdown voltage.

What is claimed is:
 1. A compound semiconductor device comprising: achip substrate; an aluminum nitride layer disposed above the chipsubstrate; and a compound semiconductor layer disposed above thealuminum nitride layer, wherein a part of a side of the chip substrate,a side of the aluminum nitride layer and a side of the compoundsemiconductor layer form an inclined surface, wherein an end face of thechip substrate is perpendicular to an upper surface of the chipsubstrate, wherein the inclined surface extends to the end face of thechip substrate, and wherein the side of the aluminum nitride layer andthe side of the chip substrate are covered by an amorphous layer or apolycrystal layer and in direct contact with the amorphous layer or thepolycrystal layer.
 2. The compound semiconductor device according toclaim 1, wherein all of the side of the compound semiconductor layerforms an inclined surface.
 3. The compound semiconductor deviceaccording to claim 1, wherein the amorphous layer or the polycrystallayer is a layer in which the aluminum nitride layer and the compoundsemiconductor layer are amorphized.
 4. The compound semiconductor deviceaccording to claim 1, wherein a surface of the chip substrate has arecess along a scribe lane, and the amorphous layer or the polycrystallayer is in direct contact with the recess.
 5. The compoundsemiconductor device according to claim 1, wherein the amorphous layeror the polycrystal layer contains at least one of silicon and aluminum.6. The compound semiconductor device according to claim 1, wherein theamorphous layer or the polycrystal layer contains silicon at not lessthan 1 at %.
 7. The compound semiconductor device according to claim 1,wherein the amorphous layer or the polycrystal layer has peaks andvalleys with an average pitch of 0.05 μm to 1.0 μm on a surface of theamorphous layer or the polycrystal layer.
 8. The compound semiconductordevice according to claim 1, wherein the chip substrate is made of anyone selected from the group consisting of silicon, silicon carbide, andsapphire.
 9. A resin-sealed type semiconductor device wherein theamorphous layer or the polycrystal layer of the compound semiconductordevice according to claim 1 is in contact with a resin agent forassembly for one of the amorphous layer or the polycrystal layer to beunder-filled or side-filled by mold resin sealing, incorporation into acomponent-incorporated substrate, or flip-chip mounting.
 10. Thecompound semiconductor device according to claim 1, wherein the compoundsemiconductor device is a power semiconductor device.
 11. A compoundsemiconductor device comprising: a chip substrate; an aluminum nitridelayer disposed above the chip substrate; a lateral semiconductorelement, in which electric current flows in parallel to the chipsubstrate; and a compound semiconductor layer disposed between thealuminum nitride layer and the lateral semiconductor element, wherein apart of the side of the chip substrate forms an inclined surface,wherein an end face of the chip substrate is perpendicular to an uppersurface of the chip substrate, wherein the inclined surface extends tothe end of the chip substrate, and wherein a side of the aluminumnitride layer is covered by an amorphous layer or a polycrystal layerand is in direct contact with the amorphous layer or the polycrystallayer.
 12. The compound semiconductor device according to claim 11,wherein the amorphous layer or the polycrystal layer is a layer in whichthe aluminum nitride layer and the compound semiconductor layer areamorphized.
 13. The compound semiconductor device according to claim 11,wherein a surface of the chip substrate has a recess along a scribelane, and the amorphous layer or the polycrystal layer is in directcontact with the recess.
 14. The compound semiconductor device accordingto claim 11, wherein the amorphous layer or the polycrystal layercontains at least one of silicon and aluminum.
 15. The compoundsemiconductor device according to claim 11, wherein the amorphous layeror the polycrystal layer contains silicon at not less than 1 at %. 16.The compound semiconductor device according to claim 11, wherein theamorphous layer or the polycrystal layer has peaks and valleys with anaverage pitch of 0.05 μm to 1.0 μm on a surface of the amorphous layeror the polycrystal layer.
 17. The compound semiconductor deviceaccording to claim 11, wherein the chip substrate is made of any oneselected from the group consisting of silicon, silicon carbide, andsapphire.
 18. A resin-sealed type semiconductor device wherein theamorphous layer or the polycrystal layer of the compound semiconductordevice according to claim 11 is in contact with a resin agent forassembly for one of the amorphous layer or the polycrystal layer to beunder-filled or side-filled by mold resin sealing, incorporation into acomponent-incorporated substrate, or flip-chip mounting.
 19. Thecompound semiconductor device according to claim 11, wherein thecompound semiconductor device is a power semiconductor device.
 20. Acompound semiconductor device comprising: a chip substrate as a base ofa compound semiconductor chip; an aluminum nitride layer disposed abovethe chip substrate; and a compound semiconductor layer disposed abovethe aluminum nitride layer, wherein a side of the aluminum nitride layeris covered by an amorphous layer or a polycrystal layer and is in directcontact with the amorphous layer or a polycrystal layer, and athickness, in a direction parallel to an upper surface of the chipsubstrate, of the amorphous layer or the polycrystal layer disposed onthe side of the aluminum nitride layer is larger than a thickness of thecompound semiconductor layer in a cross-sectional view.
 21. The compoundsemiconductor device according to claim 20, wherein the amorphous layeror the polycrystal layer is a layer in which the aluminum nitride layerand the compound semiconductor layer are amorphized.
 22. The compoundsemiconductor device according to claim 20, wherein a surface of thechip substrate has a recess along a scribe lane, and the amorphous layeror the polycrystal layer is in direct contact with the recess.
 23. Thecompound semiconductor device according to claim 20, wherein theamorphous layer or the polycrystal layer contains at least one ofsilicon and aluminum.
 24. The compound semiconductor device according toclaim 20, wherein the amorphous layer or the polycrystal layer containssilicon at not less than 1 at %.
 25. The compound semiconductor deviceaccording to claim 20, wherein the amorphous layer or the polycrystallayer has peaks and valleys with an average pitch of 0.05 μm to 1.0 μmon a surface of the amorphous layer or the polycrystal layer.
 26. Thecompound semiconductor device according to claim 20, wherein the chipsubstrate is made of any one selected from the group consisting ofsilicon, silicon carbide, and sapphire.
 27. A resin-sealed typesemiconductor device wherein the amorphous layer or the polycrystallayer of the compound semiconductor device according to claim 20 is incontact with a resin agent for assembly for one of the amorphous layeror the polycrystal layer to be under-filled or side-filled by mold resinsealing, incorporation into a component-incorporated substrate, orflip-chip mounting.
 28. The compound semiconductor device according toclaim 20, wherein the compound semiconductor device is a powersemiconductor device.